Numerous problems have been encountered by users of cured resins obtained by curing curable resin compositions, even though the electric characteristics such as the dielectric characteristic, the volume resistivity, and the insulation breakdown strength, as well as the mechanical characteristics such as bending strength, compressive strength, and impact strength, of such cured resins may be superior. For instance, when such resins are used as sealing agents for electric or electronic parts, repeated thermal shock results in the generation of gaps between the sealing resin and the part, or results in the generation of cracks in the sealing resin. This often occurs because the coefficient of thermal expansion of the resin is much greater than that of the electric or electronic part. Further, the part itself may be destroyed so that there occurs a conspicuous drop in the reliability of such parts.
Several solutions have been proposed for endowing cured resins with flexibility. In this regard, reference may be had to certain curable resin compositions of powder obtained by pulverizing silicone rubber containing linear organopolysiloxane blocks in the amount of 10 weight percent or greater, as in Japanese Patent Application Kokai No. Sho 58-219218; certain curable resin compositions of powdered silicone rubber which contain linear organopolysiloxane blocks in the amount of 10 weight percent or greater obtained by curing silicone rubber compositions in an aerosol state in a hot air draft, as in Japanese Patent Application Kokai No. Sho 59-96122; and certain curable resin compositions of powdered silicone rubber obtained by curing silicone rubber compositions in a disperse state in water, as in either Japanese Patent Application Kokai No. Sho 64-4614 or Japanese Patent Application Kokai No. Sho 64-51465.
However, even in these cases, the thermal shock resistance of resins obtained by curing the composition, has been insufficient, especially thermal shock resistance following the absorption of moisture.